Richie: The £50, 3 week Featherweight

[harry hills]

I would doubt they are anything special. Won't see much difference from a 550 and they might even be worse going on the ebay seller's description rather than the data sheet.

[Rapidrory]

Well, I'll grab a couple anyway and give it a look; given the cost I'm not too fussed if they turn out to be useless.. I'll report on how they do.
Have to say though that the 550's I have have a no load current of 0.8A at 9V, where as the 600's are quoted at 2A, so either the 600's have lower winding resistance therefore more power, or the 600's just have rubbish bearings :P

[harry hills]

Yeah good stuff. If they can at least match a 550 then I would get some.

[daveimi]

I measured the wattage of a few different drill motors at around 80 watts or so, and that data sheet talks about 110 watts give or take. I imagine it will be noticably more torquey than your 550. I think for a time Little Hitter ran Speed 600's at something like 22v and that goes like hell and quite happily shoves stuff about in the fw champ vids.

[Max]

If you want to try out something different then you could try and stick a pneumatic muscle in there, very cheap to make and could power it off a small compressor or CO2 bottle with regulator. Could make for a very cheap pneumatic setup and doesn't need to be too quick as it's just a lifter.

[Rapidrory]

Yeah, I'm only looking for something like a 50% improvement or whatever; the 550 in there works fine, it's just a little on the slow side and pretty strained lifting another robot (the lifter has a max lift of 20kg before it stalls). A bit of extra power and speed would just be nice.

I've got all the parts to make a pneumatic lifter setup like the one you described Max, but it'd be too drastic a change; the lifter I've got works very nicely so don't want to change it too much. May have a look at pneumatics in another robot; I'm currently hoping to experiment with LP pneumatic flippers made from 2 stroke engine parts at the moment :P

[Rapidrory]

Well the 3 Johnson 600's arrived. The build quality of them actually looks better than the 550's in the argos drills, so that's a good start.

They have a winding resistance of 0.2 ohms, as opposed to the 550's 1 ohm, giving it a stall current of 60A at 12v. This is understandable when you have a look at the windings; they're quite a bit thicker in the 600s, which also implies fewer windings as they're packed in the same space.

Idle current is about ~2A at 9.6V, which is what was quoted in the data sheet.

They are slightly longer than the 550, which is mostly down to the stronger bearing mounts, but there is a little extra length in the coils.

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Running on 12V, the 600 sounded about 30-50% faster, though I have no way to quantitatively test it atm.

Also seemed to have plenty of torque, though again, grabbing the output shaft with pliers is not a very accurate test. Did heat up quite quickly when put under load though.

The mounts at the front are a direct match to the 550, so the 600s can just be a drop in replacement

To summarise, these are very nice motors given the price, but I believe these are 9V motors of a similar nominal power to a 550 (relying more on current than voltage for its power). Therefore when you overvolt them to 12V you get more power, as you would overvolting a 550 on 16V. It will definitely make Richie's lifter faster (dunno about extra lifting power yet..), but that's only if they don't catch fire first... I will try installing one over the Christmas holiday.

[daveimi]

They look pretty beefy and solid.

[Rapidrory]

Can't complain for £3.50 each :P

[mrsam]

I have a couple of those Johnson motors that i was planning on using with some drill gearboxes, wasn't convinced they'd fit in with the extra bearing support though. I'll be watching with interest to see if they are an improvement, nice cheap motors.

[daveimi]

"Can't complain for £3.50 each :P"

Jobsaguddun

[Rapidrory]

After one of the ESCs burnt out at the last event, Richie's been sat in my attic as a pile of parts. However with Whitwick coming up and it being half term, I decided I should probably start putting it back together.
I've fitted those Johnson 600 motors to the drive as that was a lot easier than fitting it to the lifter with the tools I currently have. They're a little close to the actuator, but not as close as the 550s used to be before the chassis upgrade so hopefully it's fine. I'm yet to test them out so don't know yet how they perform compared to 550's.. look good so far though.
To drive these, I've got my 400A heavyweight ESC in there atm, as the Johnsons draw a lot more current than the 550's, and I don't have any other ESC suitable to drive them. I'm using this as an excuse to test out the ESC to check it hasn't got any odd hardware/firmware bugs; It's a lot less scary to discover them in a Feather then it would be to find out in my heavy :L I'll have to find/ make a new ESC for Richie in the summer when this one moves to my heavy, but it'll do for now.
Also upgraded the wiring loom to be all XT60s (rather than a few PC Molex thrown in), and upgraded the battery to a 40C 2200 mAh, and swapped the fuse for a 60A one rather than two 30A fuses in parallel. Should all be a little less... flamey..

Unfortunately it would seem that I left the baseplate at home, so I've had to throw something together using a rather flimsy piece of chipboard I found... Not really ideal, but should hold; It's only really there to keep the dust out.

Here's a pic of the current setup:

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[daveimi]

You know your heavy esc? If it got damaged at an event do you think it would be possible to return for repair? Assuming you start selling them and everything?

[Rapidrory]

Considering the low volume that would be sold then that would probably be fine, though I'm still not planning on selling them just yet... If I get some home PCB manufacturing going on then I might look into it again..

[Rapidrory]

So, having completed an event with the Johnson 600 fitted instead of 550s, I have to say they're actually pretty good! My lifter died early in the day, meaning I had to resort to being just a rambot, so the drive got some thorough testing and I was very glad they were fitted; very noticeable increase in speed, I'd say around 50%, and I was able to push people around quite nicely, which is never normally something Richie can do. The motors were rather hot at the end of the two fights I lasted the full 3 minute for (you could almost burn your hand on them), but they're 9.6v motors overvolted to 12v so that wasn't too surprising. Both were still working fine at the end of the day though, and at £3.50 each, if one does burn out eventually, I'm not gonna be too upset :L

Fitting them to the drill gear boxes only required cutting a few mm off the end of the shaft, and then grinding a flat on it to fit the cog from the 550, all of which took about 5 mins with a dremel. After that it just screwed straight in to the drill gearbox as a 550 would. All in all took about 15 mins to fit each motor in the robot. Very worth while upgrade for the money and effort required.

In other news, the new Heavyweight speed controller I had fitted in Richie for testing worked flawlessly all day without getting even slightly warm, which means I can go ahead with building my heavyweight over Easter (This was hopefully the last event I do without a heavy).

As was mentioned earlier, Richie's lifter broke. This was courtesy of Battleaxe putting me on the floor flipper in just such a way that it hurled me into the steel wall of the arena. This bent the lifting forks, arm, and linkage, and the lifter drive circuitry also burnt out (Damn you Battleaxe! *shakes fist*). Managed to get things straight enough to be used, but with the lifter circuit gone and not enough time left to fix it, the lifter was out of action for the rest of the day. I'm planning a much neater solid state switching circuit that should be much more reliable.